Cell division - cell division is the process by which a parent cell decides in two or more daughter cell.
Importance of cell division for a living cell -
- In unicellular organism cell division reproduce an entire organism.e.g amoeba
- cell division can produce the progeny from some multi cellular organism such as plants which grow from cutting.
- cell division also enables sexually reproducing organism to develop from a single cell,the fertilized egg or zygote.
- cell division involves in repairing of cells.e.g bone marrow makes the new blood cell.
- it is important because it distributes the identical genetically material to daughter cell.
- with the cell division growth occur through and increase in volume and enlargement of the outer membrane.
- without cell division death will quickly ensure.
- Genetic variation -
- Meiosis provides a part to remain the chromosomal number constant generation.
- In asexually reproduced organisms the variation among off spring occurs through mutation.
- genetic variation occurs through meiosis.
- It can produce off springs very quickly.e.g prokaryotes
- mutation is also present in sexually reproduced cell.
- Methods of genetic variation in meiosis -
- crossing over
- independent assortment of homologous chromosome
- crossing over
- exchange of genetic material between non-sister chromosomes of a bivalent during meiosis.
- average of two or three cross over in per human chromosome takes place.
- it is necessary for normal segregation e.g reduced levels of crossing over have occurred due to the extra copy of chromosome 21.